The invention relates to a ball separating device for ball throwing machines, especially squash balls or tennis balls, which is arranged in the form of a driven turntable so as to be rotatable substantially horizontally on the base of a ball storage container and has on a circumferential circle substantially vertical passages of a width somewhat greater than the diameter of the balls to be separated, these passages being kept closed at their lower ends over the extent of their circumferential path by a base surface and only opened in the region of a ball delivery point, whilst in the peripheral region of the ball delivery point at a distance equivalent to approximately one ball diameter above the base surface the passages are covered at least partially by a ball stop.
Thus the invention relates to ball throwing machines such as are commonly used in tennis training and from which balls which are held in a ball storage container are thrown out individually at intervals.
Such ball separating devices are equipped as perforated discs or star wheels with four or more passages distributed over the periphery and are set in slow rotation by a geared motor. For the separation of the balls it is necessary that during the stage in the rotation through which each passage passes between the moment of release of the ball stop after passing over the discharge opening and reaching the next ball stop a ball from the ball store enters the passage and comes to rest on the base surface. With a rapid succession of balls it can happen that as a result of bridge formation by balls accumulated in the ball storage container above the turntable a ball does not regularly enter the passage so that the ball throwing machine then has so-called misfires. This occurs particularly when the surfaces of the balls adhere strongly to one another, that is to say with roughened tennis balls or particularly with squash balls the surface of which has a high coefficient of friction. The ball throwing rhythm, which is actually determined by the rate of rotation of the turntable, is then disrupted.
When this separation principle is applied to balls with very high coefficients of friction of their surfaces, such as for example squash balls, the diffuculty also arises that a ball which is lying in a passage in the turntable and must roll down onto the base surface located below it during rotation on the turntable and must therefore slide over the walls surrounding the passage is prevented from rolling down satisfactorily by the high surface friction and is drawn into any small gap between the turntable and the base surface or in the case of an open spider even the wall surfaces and is destroyed, which leads to momentary blocking of the separating device. Therefore it is not possible for a known separating device for tennis ball throwing machines to be used for squash balls simply by adapting the dimensions.
It was also shown that in certain cases of particularly strongly adhering ball surfaces the previously known construction of the ball stop in the form of a stretched thread which crosses the passage in the peripheral region of the ball delivery point at a distance of approximately one ball diameter above the base surface can result in disruption of the ball separation. The cause of this can be the flexibility of the thread but can also be the relatively steep lead angle with which the thread enters the circumferential path of the balls located in the passages.
Reference is made to the published German patent application No. 22 62 880 to Dieter Miehlich and to the U.S. Pat. No. 4,086,903 to Jack C. Scott.